Adjustable variable displacement pump



April 1953 A w. H. DE LANCEY 2,635,551

ADJUSTABLE VARIABLE DISPLACEMENT PUMP Filed-March 18, 1948 Patented Apr. 21, 1953 ADJUSTABLE VARIABLE DISPLACEMENT PUMP Warren H. De Lancey, Springfield, Mass., assignor, by. mesne assignments, to Houdaille- Hershey Corporation, Detroit, Mich., a corporation of Michigan Application March 18, 1948, Serial No. 15,677

11 Claims. 1

The present invention relates to a variable capacity fluid pump of the vane type and, more particularly, to that type of variable capacity fluid pump in which the displacement automatically adjusts itself to compensate for variations in the driving speed or output requirements; the displacement being modulated from maximum to zero by comparatively slight increases in pressure, after reaching a predetermined point. Pumps of the abovenoted type are eachprovided with a so-called modulator ring which surrounds the pumps vanes, for the purpose of varying the output capacity as the ring shifts radially of the pump rotor in a direction opposed to the force of a biasing spring, in response to variations in the pressure of the fluid which, being exposed to the inner periphery of the ring, is efiective to exert a thrust against the ring. Such a modulator ring is usually bodily movable upon a fulcrum positioned at one side thereof within the pump chamber, so that the pressure generated by the pump on the inside of the modulator ring is unbalanced, relative to the ring fulcrum, and thus,

causes the ring to move against the spring pres-' sure. In other words, whenever the fluid pressure within the ring becomes great enough, it will overcome the force of the spring, and thereby shift the ring from an eccentric to a noneccentric position, relative to the rotor; it being understood that the spring normally urges the ring into an eccentric position relative to the rotor. Experimentation has shown that such a design is critical in certain respects. For example, the spring must be carefully calibrated, and the position of the modulator ring, relative to the rotor, carefully adjusted, so that the various forces set up by the fluid within the ring will cause the ring to shift in response to a predetermined pressure variation only. It has been found most expensive and bothersome to so calibratethe spring and adjust the modulator ring relative to the rotor, and thus in pumps heretofore employed, the mechanical and hydraulic forces set up on the modulator ring, due to these errors in calibration and alignment, have been appreciable. Furthermore, since these extraneous forces tend to vary as the pump speed and fluid temperature change, it follows that the fluid output pressure will not remain constant, for the modulator ring will swing about its fulcrum in response to divers values of hydraulic force.

It is, therefore, a primary object of the present invention to provide a variable capacity fluid pump of the above described type which is designed so that extraneous mechanical and hydraulic forces acting upon its modulator ring will not adversely aifect its fluid output pressure.

A morespecific object of the present invention is to provide such a variable capacity pump with an adjustable valve means which will be effective to supply fluid under pressure against the outer periphery of the modulator ring at a point opposite to the ring biasing spring whenever the fluid pressure increases beyond a, predetermined amount, to the end that this fluid will effectively shift the modulator ring in opposition to said spring.

A further object of the present invention is to provide such a variable capacity pump which will overcome the hereinabove noted shortcomings of the prior type pumps, but which, at the same time, may be readily and inexpensively manufactured.

With the above and other objects in view, as will hereinafter appear, the invention comprises the devices, combinations, and arrangements of parts, hereinafter set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention in which the several features of the invention and the advantage obtained thereby will be readily understood by those skilled in the art.

' In the accompanying drawings:

Fig. 1 represents a vertical elevation view of a pump unit in which the present invention is incorporated, said view being taken substantially along the line I-l of Fig. 2.

Fig; 2 represents a vertical sectional view taken substantially along the line 2--2 of Fig. 1.

Fig. 3 represents, on a reduced scale, a rear face view of the present pumping unit.

Fig. 4 represents a sectional view taken substantially along the line 4 4 ofFig. 1 with the member 45 removed.

Like reference characters refer to like parts in the different figures.

Referring particularly to Figs. 1 and 2, the present invention is incorporated in a pumping unit which comprises a housing element ll) of generally annular form and having front and rear plates ll and I2 secured over its opposite sides by means of a plurality of bolts [3, l 3 which pass through holes provided in the housing and end plates. This housing. [0 is formed with a central cylindrical aperture! which is closed over by means of the end plates I I and I2. Each of these end plates is provided with a central aperture [5 in which is rotatably journalled a rotor shaft 16 which may be driven in any suitable manner. The shaft 16 passes through the chamber I4 and carries within this chamber a pump rotor H, the latter having an inner hub portion l8 which surrounds the shaft and is keyed thereto, as shown at I9 in Figs. 1 and 2.

The pump rotor I1 is formed in the usual manner with a. series of radial slots 20, 20, in each of which is disposed a radial slidable vane 2 The outer ends of said vanes are adapted to work against the interior periphery of a ringlike member or modulator ring 22 which surrounds the rotor IT in the pump space provided by the cylindrical chamber M of the housing said modulator ring 22, as well as the several vanes 2|, 2|, extending across said space from side to side between opposite inner faces 23 and 24 of the respective end plates I and I2.

The modulator ring 22, at its outer periphery, is substantially cylindrical in shape, and has a diameter which is slightly less than the inner diameter of the bore I4 and, on the inner periphery, is appreciably larger in diameter than the pump rotor H. In consequence of this, there is ample opportunity in the pump space surrounding the rotor I! for free movement of the modulator ring 22 into positions of varying eccentricity, relative to the rotor H, to vary the pumping action of the latters slidable vanes 2 2|.

A simple and highly advantageous mounting of the member 22, for purposes of such eccentricity movements, is obtained by providing on the outside surface of the ring 22, and preferably across the entire Width, a rib 25 of substantial triangular cross section, and with said surfaces at an acute angle to each other, so as to form at their intersection a virtual knife edge, as indicated at 26. For the reception of the rib 25, the surface of the bore M, as shown in Fig. l, is provided with a two-sided indentation or cleft 21 somewhat shallower than the rib 25, and with its intersecting sides at an appreciably larger angle to each other than the intersecting side of the rib, thus, to give ample opportunity for free and frictionless rocking movements of the ring 22 on the axis afforded by the bottoming of the rib edge 26 in the angular indentation or cleft 21.

Referring particularly to Figs. 1, 3, and 4, the face 24 of the end plate l2 provides an arcuately shaped fluid intake passage or port 28 and an arcuately shaped fluid delivery or oiftake passage 29. In this latter connection, it is to be understood that the present pump unit is adapted to have the outer portion of its end plate |2 disposed over or against a casing which is provided with a pair of fluid conducting conduits or apertures, each of which is adapted to be connected with an intermediate portion of a respective one of the fluid intake and olftake passages 28 and 29, so as to conduct fluid to and from th pump unit. It is the function of these arcuately shaped passages or ports 28 and 29 to insure an unrestricted internal flow of fluid as drawn into and expelled from the space between the vanes 2 I, 2| by the rotation of the rotor l1 within the ring 22 in a direction of the arrow 30 which is associated with Fig. 1. It is to be particularly noted that neither of the apertures 28 or 23 communicate with the space defined between the outer periphery of the ring 22 and the wall of the chamber I4, 'no matter whether the ring is in its position of maximum or minimum eccentricity, relative to the rotor As may be seen from Figs. 1 and 2, the rotors inner hub portion I8 is provided w th a P ir f annular recesses 3|, 3|. Since these recesses are intersected by the inner ends of the radial slots 20, 20, it follows that the end extremities of the inner edges of the several vanes 2|, 2| are 1ocated in these face recesses 3|, 3| of the rotor Also located in each of these recesses 3|, 3| is a loose ring 32 which encircles the shaft l3, and has an external diameter that gives it peripheral contact with the inner edge portions of each of the several vanes 2|, 2| of the rotor Thus, each of the rings serves as a shiftable backing for the vanes, all in the usual manner.

In Fig. l, the modulator ring 22 is shown in its position of maximum eccentricity relative to the rotor its movement to this position being obtained by the thrust thereupon by a suitable spring 33 disposed within an opening 34 of the housing |IJ. One end of this spring engages the top portion of the opening 34 and the other end thereof is seated within a recess 35 provided in the peripheral portion of the ring 22. The pressure of the spring 33 against the ring 22 normally biases the ring about its pivot rib 25, to the end that the bottom portion of the ring will approach contacting relation with the lower portion of the bore M. It is to be understood that the spring 33 virtually floats between the ring 22 and the upper portion of the opening 34, thereby to provide a movable direction of spring thrust.

The fluid pump, as hereinabove described, is substantially the same as that disclosed in the United States patent application of De Lancey et a1. Serial No. 661,706, filed April 12, 1946, now abandoned. In a pump, as described above, if fluid in excess of the output requirements is being delivered by the pump, the resulting increase of fluid pressure in the wedge shape zone 3-; between the rotor I1 and the ring 22 becomes im mediately effective against the ring surface in said zone to move said ring against the pressure of the spring 33 toward a more concentric position, relative to the rotor 11, which position automatically reduces the pumping action of the vanes 2 2| to a point in keeping with the output requirements in a manner which is set forth in the hereinabove noted prior patent application. Thus, under all conditions, the pump will automatically adjust itself to deliver fluid under pressure only in amounts required by the device or devices which it is supplying. From the above, it is to be understood that the fluid is adapted to be drawn into the pumping unit by way of the port 23. The rotor, with its accompanying vanes 2 2 I, will, of course, increase the pressure upon this fluid and deliver the same out of the housing by way of the port 23.

As hereinabove noted, in order to operate the present described pump in a proper manner, the ring biasing spring 33 must be very carefully calibrated so that the ring will shift from its position of maximum to its position of minimum eccentricity only in response to a predetermined quantity of fluid pressure. Also, the relative positions of the modulator ring 22 and the rotor I! must be very accurately adjusted in order to insure success in the operation of the above described device, for it has been found that the various forces set up by the blades and the pumping action causes pressure variations, in the event that the position between the ring and rotor are not exactly proper. The present invention provides a pumping device in which these shortcomings are entirely eliminated in a manner as set forth hereinbelow.

Referring particularly to Fig. 1, it is to be understood that the inner peripheral portion of the housing I4 is provided, at a point diametrically opposite to its cleft 21, with a projection or fluidsealing rib 31. This fluid-sealing rib 31 extends completely across the width of the housing I4 in the same manner as does the ring rib 25. As may be particularly noted in Fig. 1, the rib 31 is adapted to engage the outer periphery of the modulator ring 22 and thus maintain, in conjunction with the spring 33, the rib 25 within its indentation or cleft 21. In order that a proper sealing contact may be had between the housing projection or rib 3'! and the periphery of the ring 22, the latter is provided with a curved surface generally designated by the numeral 38, which curved surface has its center or radius loci located substantially within the apex of the cleft 21. Thus, as the ring 22 rotates about its fulcrum rib 25, its peripheral portion 38 will remain in intimate contact with the housing projection or rib 31 which may be curved in a manner complementary to the surface 38. By referring to Fig. 2, it is to be understood that the sides of the ring 22 are each in intimate contact with a respective one of the faces 23 and 24 of the end plates l! and I2. Thus, the faces 23 and 24 guide the ring 22 and prevent any axial movement thereof, as the same is oscillated back and forth radially of the rotor ll. Also, it should be understood that the ring fulcrum rib 25 and the housing rib .31 function to divide the space between the housing H] and the outer periphery of the ring 22 into a pair of separate compartments which are designated, respectively, by the numerals 39 and 40. In this latter connection, it is to be observed that neither of these compartments or zones 39 and 40 communicates directly with either of the inlet or outlet ports 28 and 29, no matter whether the ring 22 is in its position of maximum or minimum eccentricity.

Due to the fact that the fulcrum rib 25 and housing rib 31 each extends entirely across the width of the housing I4, it will be appreciated that any fluid which collects in the zone or compartment 39 will be virtually trapped therein; it being understood that such fluid would normally find its way into this compartment from the outlet port 29. Since this fluid will be trapped within the compartment 39, the latter will function in the manner of a dashpot to dampen out the rapid oscillation of the ring 22 which may be set up whenever the varying impulses of the fluid thrust upon the ring become tuned to the natural frequency or to one of the harmonics of the ringbiasing spring 33. Such a dampening expedient is more fully described and claimed in a United States patent application of De Lancey et al. Serial No. 772,293, filed September '5, 1947, now abandoned.

Instead of using a very carefully calibrated biasing spring, the present invention contemplates the provision of a spring 33 which is of a moderate but uninfluential value, and which need not be closely calibrated in order to make the present pump Work properly. However, when such a spring is used in conjunction with a pump of the present type, some auxiliary means must be provided so that the ring 22 will only shift towards its noneccentric position relative to the rotor, in response to a fluid pressure of a predetermined value. In order to fulfill these needs, the presentend plate i2 is provided with a radially disposed bore or conduit 4 i'which leads directly from the outlet port 29 (see Fig. 4) to a second bore 42 which is disposed within the housing I0.

This bore 42 communicates directly with a third bore 43 also disposed within the housing l0. Referring particularly to Fig. 1, it is to be understood that the bore 43 is axially aligned with an enlarged bore 44 which opens up at the peripheral surface of the housing It. Disposed within the bores 43 and 44 is a piston element 45 having a pair of flanges 46 and 41, of which the latter has a diameter substantially smaller than the former.

A spring 48 abuts against one end of the piston 45, so as to force the flange .46 toward a shoulder 49 formed at the juncture of the bores -43 and 44. The other end portion of the spring 48 engages a plug 55 which is threadedly received within the open end portion of the bore 44. A duct 5| leads from the bore 44 directly to the chamber portion 39 of the housing aperture l4. From the above, it will be appreciated that due to the existence of the radial bore 4|, the fluid from the pressure side of the pump will enter the bore 43 and act against the flanges 46 and 41. However, since the flange 46 is of a greater diameter than the flange 4?, the fluid will tend to shift the piston 45 against the action of its spring 48, and it will be observed that if the piston is shifted far enough in this direction, the duct 5| will be placed in communication with the radial conduit 4|, to the end that the fluid under pressure will be delivered directly to the compartment or zone 39 which is defined by the lower peripheral portion of the ring 22 and the lower wall of the housing aperture l4. Clearly, such an influx of oil within the compartment 39 will function to shift the modulator ring 22 against the action of the spring 33, so as to position the ring in a less eccentric location, relative to the rotor I1. It is to be understood that the valve spring 48 may be so calibrated so that the piston or valve 45 will not operate until the fluid pressure at the output side of the pump has reached a predetermined value. After such a value has been reached, the valve or piston 45 will open, thereby supplying oil to the compartment 39 under pressure, to the end that the modulator ring is shifted against the force of the spring 33. Since the force of the spring 33 is more or less unconsequential, and since the available hydraulic pressure acting within the compartment 39 is relatively high, there will be no question but that the ring 22 will shift against the action of the spring 33 whenever the valve 45 is shifted to its open position. In other words, the various forces acting upon the ring are negligible compared to the available hydraulic force which exists within the compartment 39 whenever the valve is so opened. It is to be observed that the threaded member 50 is provided with a screw driver slot 50' which permits the element to be adjusted lengthwise of the bore 44, to the end that the force of the spring 43 may be adjusted. Thus, the present invention contemplates that the ring 22 may be shifted against the spring 33 in response to various predetermined fluid pressure values, depending upon the setting of the element 50.

It will also be observed from Fig. 1 that the bore 43 extends some distance beyond the flange 4'! whenever the piston 45 is in its closed position.

The space thus provided betweenthe end of the bore 43 and the flange 41 functions in the manner of a dashpot so as to prevent the piston from oscillating lengthwise of itself, in response to any pulsations that may be set up within the flow of output fluid. However, in actual operation,.the fluidfrom the pressure side, of the pressurepassage affording communication between the pressure side of the pump and the modulator ring controlling chamber'39 will shift the valve 45 initially a slight distance against the force of the spring 48, so that the valve need only shift a few thousandths of an inch in response to a predetermined fluid force in order to place the compartment or zone 39 in communication with the output port 29. Thus, the piston or valve is not normally reciprocated back and forth an appreciable distance within its bore during the operation of the pump.

In order to prevent any fluid from being trapped within the upper compartment or zone 40, and thereby preventing the proper functioning of the ring 22, the present invention contemplates the provision of a venting means. In a preferred form of the invention, this venting means comprises a radial bore or conduit 52 which is provided within the housing it), so as to communicate directly with the housing aperture H. The outer end portion of the bore 52 is enlarged and threaded, as at 53, so as to receive a vent plug 54 provided with an oil vent aperture or duct 55. From this, it will be understood that any fluid which exists within the zone at; may readily escape from the zone by way of the venting means, whenever the modulator ring 22 is shifted to a less eccentric position, relative to the rotor ll. Also, whenever the ring shifts into its eccentric position, the venting means will permit air, or any other fluid, to enter the ducts '52 and 55, to the end that the movement of the ring 22 will be substantially unrestricted.

In order to make for a smooth operating pump,

the present invention contemplates the provision within the lower portion of the housing aperture It of a pad or boss 56. It will be observed in Fig. 1 that whenever the ring 22 is in its position of maximum eccentricity relative to the rotor li, its lower portion will rest upon this narrow pad 56. Also, by referring to Fig. 2, it will be understood that this pad does not extend across the entire width of the ring but it provides a space between itself and each of the end plates i l and I2 so that the fluid from the valve 45 may flow past the pad. Thus, even though the ring is resting against the interior of the housing iii, the fluid may flow by way of the valve 45 to all parts of the compartment 39 in an unrestricted manner, to the end that the ring will be moved smoothly against the force of the spring 33. In other words, the ring area against which the fluid will act is not increased appreciably as the ring moves out of contacting relation with the bottom portion of the housing.

It is to be understood that in the event fluid from the pressure side of the pump should leak past the sides of the modulator ring and into the compartment 39, there would be a tendency for the ring to rise against the force of the spring 33, even though the valve was in a closed position. In order to prevent such an undesirable action, the opposite side portions of the ring are each provided with an arcuate groove 51 which functions to collect this fluid leakage and conduct it to the upper compartment by way of a short radial groove 58. Thus, any such fluid leakage will be collected by the grooves 51, -51 and conducted back to that side of the pump which is vented to the atmosphere so that the leakage, if any, will not adversely affect the rings movements which, in the present invention, are controlled exclusively by the relief valve.

I claim:

1. A fluid pump comprising a chambered housing, a modulator ring pivotally mounted at one side thereof within the housing chamber, a vaned rotor operable within said ring to produce the pumping action, means associated with the interior periphery of said housing and the outer periphery of said ring for definin a fluid-conflning zone Within a portion of the normal clearance space between said ring and said housing, and a passage in said housing for delivering fluid from the pressure side of said pump directly to said zone and against said ring so as to shift said ring about its pivotal mounting, and means for preventing the flow of fluid from the pressure side of said pump to said zone until the fluid pressure within said pump reaches a predetermined value, said last mentioned means in cluding a spring-biased valve disposed within said housing and interposed in said passage.

2. A fluid pump comprisin a chambered housing, a modulator ring pivotally mounted at one side thereof within the housing chamber, a vaned rotor operable within said ring to produce the pumping action, means associated with the interior periphery of said housing and the outer periphery of said ring for defining a fluid-confining zone within a portion of the normal clearance space between said ring and said housing,

and a passage in said housing for delivering fluid from the pressure side of said pump to said zone and against said ring so as to shift said ring about its pivotal mounting, and means for con trolling the flow of fluid from the pressure side of said pump to said zone so that the fluid will flow only when the fluid pressure Within the pump is at a predetermined value, said last mentioned means including a spring-biased valve piston and a bore slidably containing the valve piston, the bore being within the peripheral wall portion of said housing and outside the confines of the housing chamber and intersecting said passage.

3. A fluid pump, comprising, a chambered housing, a modulator ring pivotally mounted at one side thereof within the housing chamber, a vaned rotor operable within said ring to produce the pumping action, yieldable means operatively engaging the outer periphery of said ring for urging said ring about its pivotal mounting to a position eccentric with said rotor, means associated with the peripheries of said housing chamher and said ring for defining a fluid-confining zone Within a portion of the normal clearance space between said chamber periphery and said ring at a location diametrically opposite to that of said yielding means, means for delivering fluid from the pressure side of said pump to said zone andagainst said ring only when the pressure of the fluid reaches a selective predetermined value comprising a passageway disposed entirely in said housing and including a bore traversing the passageway and having a slidable pressure sensitive plunger valve therein controlling flow through the passageway, and means associated with said last mentioned means for selectively predetermining the pressure at which the fluid is delivered to said zone and against said ring.

4. A fluid pump, comprising, a chambered housing, a modulator ring disposed within the housing chamber with the outer ring periphery spaced inwardly of the chamber periphery ther by to form a clearance space therebetween, a p votal mounting for said ring disposed at one side of said ring and within the clearance space, a vaned rotor operable within said ring to produce the pumping action, spring means operatively engaging the outer periphery of said ring for urgingsaid ring about its pivotal mounting to a position eccentric with said rotor, sealing means disposed within the clearance space at a location diametrically opposite to that of said pivotal mounting for cooperating with the latter element in dividing said clearance space into first and second compartments, said first compartment being located diametrically opposite said ring biasing spring, a ring-engaging pad disposed upon the periphery of the housing chamber'and within the confines of said first compartment for preventing said'ring from sealing off portions of said first compartment when said ring is in a position eccentric to said rotor, said pad being of less width than said ring, means including a spring-biased valve for delivering fluid from the pressure side of said pump to said first compartment and against said ring only when the pressure of the fluid within the pump reaches a selective predetermined value, and means for adjusting the tension of the valve biasing spring for predeterminin the pressure at which the fluid is delivered to said first compartment and against said ring.

5. A fluid pump, comprising, a chambered housing including opposing faces providing op-' posite sides of a chamber therein, a modulator ring pivotally mounted at its periphery within the housing chamber with the opposite side faces of the ring slidably engaging the opposing faces of the chamber, a vaned rotor operable within said ring to produce the pumping action, spring means operatively engaging the outer periphery of said ring for urging said ring about its pivotal mounting to a position eccentric with said rotor, means associated with the peripheries of said housing chamber and said ring for defining first and second compartments within a portion of the normal clearance space between said chamber periphery and said ring, said first compartment being located diametrically opposite said ring biasing spring, means for deliverin fluid from the pressure side of said pump to said first compartment and against said ring thereby to bias said ring about its pivotal mounting and. against the force of said spring, the opposing faces of the housing and ring having a passage therein adjacent said first compartment for collecting that fluid which escapes about the ring side portions and delivering such fluid to said second compartment, and means ventin said second compartment.

6. A fluid pump, comprising, a chambered housing including opposing faces providing opposite sides of a chamber therein, a modulator ring pivotally mounted at its periphery within the housing chamber with the opposite side portions thereof slidably engaging the opposing faces of the chamber, a vaned rotor operable within said ring to produce the pumping action, spring means operatively engaging the outer periphery of said ring for urging said ring about its pivotal mounting to a position eccentric with said rotor, means associated with the peripheries of said housing chamber and said ring for defining first and second compartments within a portion of the normal clearance space between said chamber periphery and said ring, said first compartment being located diametrically opposite said ring biasing spring, means for delivering fluid from the pressure side of said pump to said first compartment and against said ring thereby to bias said ring about its pivotal mounting and against the force of said spring, grooves i 10 formed in the opposite side portions of said ring adjacent said first compartment for collecting that fluid which escapes about the ring side portions, said grooves being in direct communication with said second compartment for delivering to the latter compartment the fluid so collected, and means venting said second compartment.

7. A fluid pump, comprising, a chambered housing including opposing faces providing opposite sides of a chamber therein, a modulator ring pivotally mounted at its periphery within the housing chamber with the opposite side portions thereof slidably engaging the opposing faces of the chamber, a vaned rotor operable within said rin to produce the pumping action, spring means operatively engaging the outer periphery of said ring'for urging said ring about its pivotal mounting to a position eccentric with said rotor, means associated with the peripheries of said housing chamber and said ring for defining first and second compartments within a portion of the normal clearance space between said chamber periphery and said ring, said first compartment being located diametrically opposite said ring biasing spring, means including a spring-biased valve for delivering fluid from the pressure side of said pump to said first compartment and against said ring only when the pressure of the fluid reaches a selective predeter mined value, means for adjusting the tension of the valve biasing spring for predetermining the pressure at which the fluid is delivered to said first compartment, grooves formed in the opposite side portions of said ring adjacent said first compartment for collecting fluid which escapes about the ring side portions, said grooves being in direct communication with said second compartment for deliverin to the latter compartment the fluid so collected, and means venting said second compartment.

v8. In combination in a fluid pump a housing comprising a ring and opposite cover plates, the housing defining a circular chamber, a modulator ring of smaller diameter than said chamber pivotally mounted at one side in said chamber, said modulator ring together with said plates defining a pump chamber within the ring, a rotor of smaller diameter than said pump chamber rotatable on a fixed axis within said pump chamber and having radial reciprocable vanes in operative pumping engagement with the internal Wall of the modulator ring defining said pump chamber, means normally biasing the modulator ring about its pivot toward one side of the housing chamber, means cooperating with the modulator ring at the diametrically opposite side thereof from and cooperating with the pivot for dividing the space between the modulator ring and the housing ring into separate compartments, a passageway extending through one of said plates and through said housing ring from the high pressure side of the pump to the compartment toward which the modulator ring is biased for subjecting the modulator ring directly to pump pressure for shifting the same pivotally against the biasing mea s, and means for controlling the delivery of pressure fluid from the pump to said compartment including a bore within said housing ring intersecting said passageway and slidably housin a plunger type control valve, said bore opening from the periphery of the housing ring for assembly of the valve into the bore.

9. In combination in a fluid pump a housing comprising a ring and opposite cover plates, the housing defining a circular chamber, a modula- 11 tor ring of smaller diameter than said chamber pivotally mounted at one side in said chamber, said modulator ring together with said plates defining a pump chamber within the ring, a rotor of smaller diameter than said pump chamber rotatable on a fixed axis within said pump chamher and having radial reciprocable vanes in operative pumping engagement with the internal wall of the modulator ring defining said pump chamber, means normally biasing the modulator ring about its pivot toward one side of the housing chamber, means cooperating with the modulator ring at the diametrically opposite side thereof from and cooperating with the pivot for dividing the space between the modulator ring and the housing ring into separate compartments, a passageway extending through one of said plates and through said housing ring from the high pressure side of the pump to the compartment toward which the modulator ring is biased for subjecting the modulator ring directly to pump pressure for shifting the same pivotally against the biasing means, and means for controlling the delivery of pressure fluid from the pump to said compartment including a bore within said housing ring intersecting said passageway and slidably housing a plunger type control valve, said bore opening from the periphery of the housing ring for assembly of the valve into the bore, the outer end of said bore bein closed by a screw plug and an adjustment spring being interposed between the screw plug and the plunger valve and adjustable as to tension by screwing the plug in or out in the outer end of the bore.

10. In combination in a variable displacement fluid pump, a housing, the housing having a chamber therein, a modulator member having a pump chamber therein and being movable within said housing chamber, a varied rotor on a fixed axis in the pumping chamber of the modulator, high pressure and low pressure ports in said housing communicating with the pumping chamber, and means for controlling the position of the modulator member to determine the displacement of the pump comprising a passage communicating with the high pressure port and directly with one side of the modulator member, said passage having a plunger valve therein responsive to prede- 12 termined fluid pressure from the pump for controlling the delivery of the fluid pressure to the side of the modulator member, one end of the plunger valve having a dashpot control structure for preventin hunting movements of the valve member.

11. In combination in a variable displacement pump including a housing defining a chamber, a modulator biased in one direction in said housing chamber, the modulator havin a pumping chamber therein, a vaned rotor on a fixed axis normally eccentric within the modulator chamher, said housing having a passage connecting the pressure side of the pump with the portion of the housing chamber toward which the rotor is eccentrically disposed, the housing having a bore therein intersecting the passage and having a reduced diameter portion at the upstream side of the intersected passage considered with respect to the direction of pressure fluid through the passage, and a reciprocable plunger valve in said bore having a large diameter portion sensitive to pressure fluid and a small diameter portion aifording a space with the wall of the bore and terminating in a flange slidably engaging adjacent the terminus of the small diameter portion of the bore to define a dashpot means resisting precipitate movement of the plunger valve and avoiding hunting thereof under the influence of the pressure fluid, said valve being normally biased to close the passage against the pressure fluid but being urged by predetermined pressure fluid pressure to open the passage.

WARREN H. DE LANCEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,943,929 Rayburn Jan. 16, 1934 2,236,556 Wunderle Apr. 1, 1941 2,238,062 Kendrick Apr. 15, 1941 2,262,331 MacNeil Nov. 11, 1941 2,433,484 Roth Dec. 30, 1947 FOREIGN PATENTS Number Country Date 489,955 Great Britain Aug. 5, 1938 528,950 Great Britain Nov. 11, 1940 

